1-benzyl-hexahydroisoquinolines and preparation thereof



Patented Apr. 7, 1953 r l-BENZYL-HEXAHYDROISOQUINOLINES v I AND PREPARATION THEREOF Joseph Hellerhach, Basel, Switzerland, assignor to Hoffmann-La Roche Inc., Nutley, N. J.,acor- V poration of New Jersey 1 No Drawing. Original application May 27, 1950, Serial No. 164,849. Divided and this applica! tion September 10, 1951, Serial No. 245,987. In Switzerland July 29, 1949 em-rmsmes PATENT OFFICE 11 Claims. ((Jl."260-"--283) I I This. invention relates to derivatives of mor- It has been found, according to this invention, phinanef and salts thereof and, also to inter-:- that morphinane and the derivatives thereo; mediatesfused in the manufactured said decan be prepared according to a process which rivatives and saltsthereof, as well as to processes may be represented by the followingforinu lae for the manufacture of these compounds. scheme:

N-CH:

is new as well as compounds of the general I yl-ethylamine (I) which itself may be obtained either from cyclohexen (1) yl acetonitrile (Harding, Haworth, Perkin, J. Chem. Soc. (London), vol. 93, year 1908, pages 1945,1956) or from cyclohexen (1) yl acetamide (Wallach, Liebigs Annalen der Chemie, vol. 347, year 1906, page 328; Liebigs Annalen der Chemie, vol. 353, year 1907, page 292; Darzens, Rost, Comptes Rendus, vol. 153, year 1910, page 774) by reduction with lithium aluminium hydride.

According to the present invention the amine (I) is reacted with phenyl-acetic acid or a substituted phenyl-acetic acid (II) to form the corresponding phenyl-acetic acid (cyclohexenylethyl) -amide (III). This latter compound is converted under cyclization into the corresponding 1 benzyl 3,4,5,6,7,8- hexahydroisoquinoline (IV), this conversion being suitably performed by means of condensing phosphorus compounds, such as phosphorus pentoxide or phosphorus halides. The methylation of IV into the N-methylated octahydro compound (VII) may be performed in various ways:

(0) Upon treating a 1 benzyl 1,2,3,4,5,6,7,8'-'

octahydroisoquinoline (VI) with ethyl formate, the formyl compound (VIII) is formed, which yields, when reduced by means of lithium aluminium hydride, the corresponding 1- benzy1-2-methyl-octahydroisoquinoline (VII).

The 1 benzyl 2 methyl octahydroisoquinolines (VII) are converted into the N-methylmorphinanes (IX) by heating with acid cyclizing 4 agents, such as phosphoric acid or hydro halic acids and the like. If the reaction is at the same time performed in a suitable manner, a hydrolyzation of the methoxy to free hydroxy groups may be effected. Free hydroxy groups (of the hydroxyor the dihydroxy-N-methylmorphinane respectively) can be methylated or acetylated.

The compounds or the salts thereof, which are obtained according to the present process, are effective as analgesics.

In the following examples parts means parts by weight unless otherwise stated.

OYoLoHExEN- (1 -YL-ETHYLAMINE (a) From cyclohemen- (1 -yZ-acetamide 139 parts of cyclohexenyl-acetamide are added in' portions, with stirring and ice-cooling, to a solution of '76 parts of lithium aluminum hydride in 6000 parts of water-free ether, the addition being conducted under nitrogen. The reaction mixture is allowed to stand for 6 hours at room temperature and thereafter kept boiling for 15 minutes. Afterwards the excess of lithium aluminum hydride is decomposed slowly with water and concentrated sodium hydroxide is added dropwise until the ether solution becomes completely clear. The ethereal solution is decanted from the lithium and aluminum hydroxide and the residue is washed twicewith 150 parts of ether each time. The united ether solutions are dried with potassium carbonate and concentrated, and the amine is distilled in the vacuum of the water-jet pump. (Boiling point 75-78 C. under a pressure of 15 mm.)

(b) From cyclohewen- (1 -yZ-acetonitrile 121 parts of cyclohexenyl-acetonitrile dissolved in 800 parts of water-free ether are added drop- Wise, with stirring, to a solution of 42 parts of lithium aluminum hydride in 2000 parts of waterfree ether, the addition being performed at 0 C. under nitrogen; stirring is continued for 2 hours at 0 C.

After decomposition of the excess of lithium aluminum hydride with water and addition of concentrated sodium hydroxide, the reaction product is isolated according to the method described in part (a) of this example.

EXAMPLE 2 N -METHYLMOBPHINANE 'Io' av solution of 125 parts of cyclohexenylethylamine in 250 parts of benzene are added slowly, with stirring and ice-cooling, parts of phenyl-acetic acid chloride in 170 parts of hen-- zene. Thereafter the reaction product is allowed to stand for 30 minutes at room temperature and heated for additional 30 minutes on a water-bath. The cyclohexenyl-ethyl-amine-hydrochloride is separated by filtration, the filtrate is washed with sodium hydrogen carbonate and water, and the solvent is distilled 01f the residue which solidifies quickly is phenyl-acetic acid (cyclohexen-(1)-ylethyl) -amide. The raw material melts at 52-55 C., after recrystallization from a mixture of henzene and petroleum ether at 69-70" C., and boils at 160 C. (temperature of the oil-bath) under a pressure of 0.01 mm.

243 parts of phenyl acetic acid (cyclohexenylethyl) -amide are heated in an oil-bath together with 1200 parts of benzene and 730 parts of phosphorus pentoxide at C. for 45 minutes and thereafter left standing for 2 hours at room temperature. Ice is then added with cooling to the reaction mixture, and the aqueous part is separated from the benzene. Upon addition at C. of solid potassium hydroxide to the aqueous part, a base separates and is taken into ether. The ether solution is dried, the solvent is driven off and the 1-benzyl-3,4,5,6,7,8-hexahydroisoquinoline is obtained as an oil. The same product is formed by phenyl-acetic acid (cyclohexenylethyl) -amide being boiled for 3 hours with phosphorus oxychloride in benzene.

The raw material is dissolved in.80 parts of water-free acetone, to this solution is added a mixture of 200 parts of methyl-bromide and 320 parts of water-free acetone and the whole is allowed to stand at room temperature for 12 hours. The residue, which remains after the acetonehaving been removed in vacuo at room temperature, is dissolved in water and extracted with ether. The aqueous solution of the quaternary salt is hydrogenated in a pressure autoclave for 19 hours together with a concentrated solution of 56 parts of potassium hydroxide in methanol in the presence of Raney nickel, at room temperature and under a pressure of 50 atm. The hydrogenation product i freed from the catalyst by filtration and the methanol is substantially removed by distillation. It is taken into benzene and the benzene solution is washed with water. After distilling off the benzene, there remains an oil which is l-benzyl-Z-methyl-1,2,3,4,5,6,7,8- octahydroisoquinoline. Boiling point 106-108 C. under a pressure of 0.01 mm.; melting point of the hydrochloride 195-196 C.

. 241 parts of 1-benzyl-2-methyl-octahydroisoquinoline which have been purified over the hydrochloride, are heated for 70 hours at 140-150 C. with 720 parts of 100 per cent. phosphoric acid. After cooling down, the reaction mixture is dissolved in 1000 parts of ice-water, adjusted to a Weak phenolphthalein-alkaline reaction by means of concentrated ammonium hydroxide and extracted with benzene. After evaporation of the benzene, the remaining N-methyl-morphinane is distilled in high vacuo. Boiling point 118-120 C. under a pressure of 0.04 mm. Melting point of the phosphate 141-145 C.

EXAMPLE '3 3-HYDROXY-N-METHYL-MORPHINANE 125 parts of cyclohexenyl-ethylamine are mixed up with 300 parts of benzene. To this mixture is added within 30 minutes a solution of 92.3 parts of p-methoxy-phenyl-acetic acid chloride in 92 parts of benzene. The reaction starts immediately and cyclohexenyl-ethylamine-hydrochloride separates. After having been stirred up at room temperature for additional 2 hours, the cyclehexenyl -ethylamine hydrochloride is separated by filtration. The benzene solution is'washed with water, the benzene is distilled off, and the residue is crystallized from petroleum ether (boiling range 80-120 C.). The p-methoxyphenyl-acetic acid (cyclohexenyl-ethyl)amide melts at 79-81 C.

2'73 parts" of p-methoxy-phenyl-acetic acid (cyclohexenylethyl)-amide are dissolved in 1000 parts of benzene andboiled under reflux for 3 hours together with 307 parts of phosphorus oxychloride. After cooling down, the excess of phosphorus'oxychloride is decomposed by means of ice-water, and the hydrochloride of l-(pmethoxy-benzyl)'3,4,5,6,'7,8 hexahydroisoquinoliner which is relatively ,diflicultly soluble in water, is extracted from the benzene with water. The aqueous solution is made alkaline by means of about 30 per cent aqueous sodium hydroxide, the precipitated base is taken up in ether, the

ether solution is dried with potassium'carbonate and then concentrated.

The remaining l-(p-methoxybenzyl)-3,4,5,6, 7,8-hexahydroisoquinoline (approximately 220 parts) is dissolved in 5 times its quantity of methyl alcohol and hydrogenated in the presence of v50 parts of Raney nickel. After no more hy: drogen is taken up, the solution is freed from the catalyst and acidified so far as just to become acid to congo by means of parts of 48 per cent hydrobromic acid. After removal of methyl alcohol, the crystalline residue is recrystallized from water. The hip-methoxy-benzyl)-1,2,3,4,5,6,7,8

octahydroisoquinoline-hydrobromide melts at,

slight pressure in the presence of 100 parts of Raney nickel. The calculated amount of hydrogen is absorbed quickly. The catalyst is then separated, and the methyl-alcoholic solution is adjusted to a weak congo acid reaction by means of concentrated hydrochloric acid. The methanol is driven off, the residue is dissolvedin water, the base is separated by the addition of ammonium hydroxide and it is taken up in benzene. After having been freed from the benzene, the base is distilled in high vacuo. The l-(p-methoxy-benzyl) -2-methyl-1,2,3,4,5,6,7,8 octahydro isoquinoline boils at 117-119 C. under a pressure of 0.003 mm. The oxalate melts at 163-164 C.

The same product is formed when, after the reaction with formalin, the p-methoxy-benzyloctahydroisoquinoline is heated with formic acid.

2'71 parts of l-(p-methoxy-benzyl)-2-methyl- 1,2,3,4,5,6,7,8-octahydroisoquinoline are dissolved in 1500 parts of 100 per cent; phosphoric acid and heated for 70 hours at -150" C. Thereafter, the mixture is cooled down, dissolved in 1000 parts of ice-water and the solution is adjusted to a weak phenolphthalein-alkaline reaction by means of concentrated ammonium hy droxide. The 3-hydroxy-N-methyl-morphinane which separates (the methyl ether has been mostly hydrolized by the heating with phosphoric acid) is taken up in a mixture of benzene-butanol (1:1) and the raw base is obtained by concentrating and boiling up with acetone. The base is purified over the hydrobromide which melts at 193-195 C. The 3-hydroxy-N-methyl morphinane has a melting point of 251-253 C. and the tartrate melts at 147 C.

3-methoxy-N-methyl-morphinane, which is yielded by 'methylation of the 3-hydroxy com pound, melts at 81-83 C., and the hydrobromide thereof has a melting point of 91-93 C. The hydrobromide of the corresponding 3-acetoxy derivative melts at 210-212 C., or, with water of crystallization, at -159 0., whereas the free base has its meltingpoint at 6841090. .1.

125 parts of cyclohexenyl-ethylamine and 196 parts of homoveratric acid are boiled in 1200 parts of xylol, whereby the water which separates is gradually'taken off by means of a water-separator. After the calculated amount of water having been separated (about 5 hours), the reaction product is left to crystallize and the crystallized amide which forms long needles is filtrated and washed with petroleum ether. After recrystallization from petroleum ether, the homoveratric acid (cyclohexen (1) yl ethyl) amide melts at 96 C. 303 partsof homoveratric acid (cyclohexenyl-ethyl)-amide are dissolved in 1500 parts of benzene and boiled under reflux for 3 hours with 183 parts of phosphorus oxychloride, whereby a salt, which is insoluble in benzene, gradually separates in a crystalline state. The crystallization is completed by the reaction product being allowed to stand for two hours at C. The crystals are separated by filtration. The precipitate is dissolved in water and made alkaline with ice-cooling by means of approximately 30 per cent. aqueous potassium hydroxide. The base which separates is taken up in ether. The ethereal solution is dried and concentrated.

The same hexahydro base is yielded when the homoveratic acid (cyclohexenyl-ethyl)-amide is heated in an oil-bath for 45 minutes at 90 C. with phosphorus pentoxide in benzene.

The. 1 (3,4' dimethoxy-benzyl) 3,4,55,73-

hexahydroisoquinoline (approximately 240 parts) is dissolved in 5 times. its amount of methyl alcohol and is hydrogenated in the presence of 80 parts of Raney nickel-paste. After the absorption of hydrogen is completed, the catalyst is separated by filtration, the methanol is distilled off in vacuo, the residue is dissolved in about 300 parts of isopropylalcohol, and the solution is adjusted to a congo acid reaction by means of 48 per cent. hydrobromic acid. The l-(3,4-dimethoxybenzyl) -1,2,3,4,5,6,7,8 octahydroisoquinoline-hydrobromide precipitates, is filtered and recrystallized from methanol. It melts at 235- 236" 0., whereas the hydrochloride has a melting point of l98-200 C. 1 A, solution of 367 parts of l-(3',4,'-dimethoxybenzyl) -1,2,3,4,5,6,7,8-octahydroisoquinoline-hy drobromide in water is adjusted to a phenolphthalein-alkaline. reaction with concentrated aqueous sodium hydroxide. The precipitated base is taken up in ether, the ether solution, is dried and concentrated. The residue, which is the free dimethoxybenzyl-octahydroisoquinolinebase, is dissolved inw 880 parts of methanol. The solution formed is allowed to stand overnight with 128 parts of 40 per cent. aqueous formaldehyde and thereafter hydrogenated in the preence of 110 parts of Raney nickel. After the absorption of the calculated amount of hydrogen, the hydrogenation stops. The methanolic solution is separated from the catalyst and freed from the methanol in a slight vacuo. In order to liberate the base from water, the residue is dissolved in benzene and concentrated in vacuo, and this operation is repeated several times. The 1- (3',4'-dimethoxy-benzyl) -2-methy1-1,2,3,4,5,6,- 7,8-octahydroisoquinoline is distilled in high vacuo. Boiling point 135 C. under a pressure of 0.001 mm. The hydrochloride melts at 229 C., the oxalate melts at 125-127 C.

8;; v This same base can be obtained in twe other ways:

(a) Upon reacting 1 (3',4' dimethoxybenzyD- hexahydroisoquinoline with methyl-bromide in acetone, the quaternary salt is formed, which, when workedrup and hydrogenated in a manner similar to that described in Example 2,

' yields the. N -methylated octahydro base.

(0) Upon heating'the 1-(3',4'-dimethoxybenzyl 1,2,3,4,5,6,7,8-octahydroisoquinoline with ethyl formate, the corresponding formylamine compound melting at 92-93 C. is formed, which, when reduced by means of lithium aluminium hydroxide, also yields the N-methylated octahydro base.

301' parts of l-(3,4'-dimethoxybenzyl)-2- methyl-1,2,3,4,5,6,7,8-octahydroisoquinoline are dissolved in 900 parts of per cent. phosphoric acid and the mixture is heated for 70 hours at -150 C. The reaction product is then cooled down, dissolved in 1000 parts of ice-water and made weakly alkaline by means of concentrated ammonium hydroxide. The precipitated base of the 3,4- (or 2,3) -dihydroxy-N-methyl-morphinane (the methyl ether is mostly hydrolized by the heating with phosphorus acid) is taken up in ether and, after the ether having been removed, it is purified over the salicylate which has its melting point at 176-180 C. The 3,4(0r 2,3)-dihydroxy-N-methyl-morphinane is crystallized from ethyl acetate and has a melting point of 246-2 5? C. The hydrobromide, which is difiicultly soluble in water, melts at 248-250 C.

This application is a division of my copending application Ser. No. 164,849, filed May 27, 1950.

I claim:

1. A compound selected from the group consisting of those having the general formula 9 10 10. A process of preparing a compound having wherein R, and R' are selected from the group the formula consisting of H and OCHs radicals.

/\ 11. A process which comprises subjecting a compound having the formula {W 5 N (g m H NH 2 c 5H2 fill wherein R." and R are selected from the group consisting of H and OCH3 radicals which com- A prises subjecting to the action of a phosphorus wherein R and Rm e s cted from the group halide c cl'zin -deh dratin a cut a com ound y 1 g y g g p consisting of H and OCI-Ia radicals to dehydrahavmg the formula tion-cyclization by heating said compound. with an agent selected from the group consisting of phosphorus pentoxide and phosphorus halides.

JOSEPH HELLERBACH.

No references cited. 

9. 1-BENZYL-3,4,5,6,7,8-HEXAHYDROISOQUINOLINE. 